Heater turns to cold air when car is idling

Tiny
ELI ZUKOKAS
  • MEMBER
  • 2007 SATURN AURA
  • 3.6L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 192,000 MILES
Went out to start it the other day let it warm up turn the knobs to heat came out after 15 minutes and it was freezing cold air. Popped the hood checked the fluid level it appeared to be fine. So I drove to work and immediately realized heat worked at acceleration but it would stop at idle.
Wednesday, October 30th, 2019 AT 8:58 PM

7 Replies

Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello,

Okay, so are you talking about the fan coming on or are you talking about the heater itself? I am thinking that this could be a problem with the electrical connector going to the blower motor, but will wait for your answer to diagnose the problem further.

Thanks,
Alex
2CarPros
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Thursday, October 31st, 2019 AT 3:52 AM
Tiny
ELI ZUKOKAS
  • MEMBER
  • 4 POSTS
It will blow air regardless on all settings, but at idle the heat will turn to cold.
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Thursday, October 31st, 2019 AT 4:19 AM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

Does this happen just when you first start the vehicle, or even after driving it for a while and then stop and come to an idle?

Thanks,
Alex
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Thursday, October 31st, 2019 AT 9:48 AM
Tiny
ELI ZUKOKAS
  • MEMBER
  • 4 POSTS
From start.
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Thursday, October 31st, 2019 AT 11:23 AM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

It takes a little bit for the engine to warm up the coolant for the heater or the defroster to blow hot air. The way the heater/defroster in a vehicle works is there is a box under the dashboard with a small radiator in it. This is connected to the cooling system and engine coolant passes through it and this is where the heat comes from. A thermostat in the engine keeps the coolant in place and won't let it circulate until it reaches a pre-determined temperature, usually around 180-190 degrees. Until the coolant reaches this temperature and circulates you will not have full heat coming from your heater/defroster. This is normal in all vehicles and nothing to worry about.

Thanks,
Alex
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Thursday, October 31st, 2019 AT 1:08 PM
Tiny
ELI ZUKOKAS
  • MEMBER
  • 4 POSTS
But it does it at idle even after the car has heated up. It will blow heat while driving but soon as I let off the gas it cools down.
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Thursday, October 31st, 2019 AT 1:31 PM
Tiny
SCGRANTURISMO
  • MECHANIC
  • 4,897 POSTS
Hello again,

Okay, this sounds like your vehicle's water pump could be going out. In the diagrams down below I have included the instructions for the removal and installation of your vehicle's water pump from the vehicle manufacturer. Please go through these guide and get back to us with how everything turns out.

Thanks,
Alex
2CarPros
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Thursday, October 31st, 2019 AT 2:25 PM

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